Making color images complete black and white

I’ve made a few attempts to engrave a ski resort trail map into wood, acrylic, etc. I’m finding that the black runs look much more sharp than blue and greens, likely because the laser sends more power in blacks than colors when processing photos. I believe I need to make all of the trails, lettering, etc in black. I’ve tried increasing the contrast and brightness but the greens still show up much less dark than the blacks in my engraving.

I’m wondering if anyone knows a photo method in lightburn, or software tool in GIMP that can achieve what I’m looking to do.

Given that lasers produce only different levels of “burn”, starting with a monochrome image will help visualize what will happen.

This is the result of desaturating the colors into a monochrome image, then posterizing it to four levels, which is about as many different values you can expect in a “grayscale” / non-dithered image:

Pretty obviously, persuading the text to be full black will dramatically improve the results.

Dithering everything other than the text will be easier than trying to get good grayscale results.

The image may be too complicated to produce visually good results, no matter how much post-processing you apply, because what works well with colors on white paper generally does not translate to grayscale.

This is where Photoshop, GIMP, Corel PhotoPaint, and any number of other photo/bitmap editors will be most helpful. Simply desaturating an image will yield grayscale, but it’s not likely to give you the contrast that you need. Using the photo-editing software to get a good high-contrast image before importing to LB is likely a more efficient and productive workflow.

To get the best conversion to what you want might require working with the individual color channels (R, G, and B) within the photo-editing software.

Thanks guys. It does look like I’ll either have to do some heavy editing or simply source a pure black/white version of the original.

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